The present invention relates to mechanisms useful in drawing blood from an arterial pressure monitoring line. More particularly, the invention relates to a pump storage mechanism adapted to reverse the flow and temporarily store fluid in an arterial line to facilitate drawing uncontaminated blood through the arterial line.
Arterial and venous infusion lines are used to inject fluids into patient's bloodstream. Various types of devices have long been used to regulate the flow of fluid from a supply container to the injection site. As is well known to health care practitioners, the flow of fluid from the supply can be turned off and blood allowed to flow in the reverse direction through the arterial line to facilitate taking periodic blood samples. The frequency of such blood samples may vary in accordance with the nature of the patient's illness and other factors. In some cases, blood may need to be drawn on a daily or hourly basis. Where the frequency of such sampling is greater, the need to safely and efficiently draw blood, without waste, becomes greater. In certain cases, such as in the case in neo-nates, which have a more limited blood supply than adults, the need to avoid unnecessary discharging of blood is particularly significant.
Contemporary mechanisms for drawing blood from an arterial line utilize a plurality of stopcock mechanisms that preclude the flow of fluid from the fluid supply and allow blood to flow from the patient into a collecting syringe connected to a removal port formed in one of the stopcocks. Such mechanisms typically require that the person drawing the blood remove two samples from the removal site in the arterial line. The first sample, generally approximately 5 milliliters in volume, potentially includes the supply fluid in the arterial line downstream of the removal port. Thus, that sample must be discarded before a representative blood sample is obtained at the removal port. In order to insure that all of the supply fluid is removed from the line between the removal site and the patient, enough fluid is typically removed such that some of the patient's blood is also discharged in the process. After the initial sample has been discharged, the second sample is typically obtained which includes the blood to be tested.
Aside from the unnecessary loss of blood, the contemporary two sample process potentially introduces other undesirable effects relating to such problems as the potential introduction of air into the arterial line and potential introduction of contaminants into the blood supply. The two step process also requires substantial effort on the part of the nurses or other clinicians who must draw the blood sample.
The present invention is directed to a mechanism for eliminating the need to undertake such a two step process to withdraw blood through an arterial line. As described in more detail below, the present invention comprises a combination pump/storage mechanism which accomodates the return flow of the downstream fluid such that a single sample may be taken from the removal port, with that sample being clear of supply fluid and therefore representative of the patient's blood supply.